Last week we had a seemingly minor story about Blizzard expanding cross server group finding. When the process is complete, all North American servers will be combined for the purposes of random PVP battlegrounds, and servers will be split into four groups of battlegroups for the purposes of the dungeon finder.
The thing I find interesting about this story is that it's seemingly a step towards a single global server for the game. WoW already supports cross-server chat with members of your random instance group, and I don't see any technical reason why the game couldn't eventually allow players to type "/invite playername servername" to add their friends from any server in the region, if not the world, to their groups. One might imagine that allowing players to actually PLAY with their friends would be great way to encourage the use of Battle.net as a social networking platform (which appears to be a major goal over at Acti-Blizzard).
Such a transition would not come without cost. Server communities would have less and less meaning, though even the current limited cross-server-dungeon-finder has already started us down that path. There is in principle a lore issue with allowing Alliance and Horde players to team up (though both sides tend to kill the exact same foes in the exact same dungeons). Perhaps most important to Blizzard, the lucrative paid character transfer services would be much less attractive if they were not necessary to switch over to the server where your friends are playing.
Then again, helping players meet up with their friends may be worth far more in the long run, as a way to keep players involved in the game and actually wanting to come back and pay more subscription fees. As the technological barriers come down, it will be very interesting to see whether Blizzard thinks the price is worthwhile.